TOC package

The TOC is divided into three layer:

TOCTree
TOCTree is a tree structure which contains TreeNode. It defines the low level. 
 
TreeView
It is a view of the TOC tree. It contains ViewNode which is wrapper of the TreeNode. Each TOCView contains a 
TreeViewFilter which defines the visibility of each TreeNode in the parent.

TOCView
It is a localized TreeView.